class_docstr: Patch a callback output value
  
  Act like a proxy of the output prop value on the frontend.
  
  Supported prop types: Dictionaries and lists.
code: def __getitem__(self, item):
      validate_slice(item)
      return Patch(location=self._location + [item], parent=self)
  
label_desc: Use image node_id 4 for calling the Patch obj's underlying member method code with example usage: obj.__getitem__(item) and returns: Patch